SV IMM 9mm Major test fire...

[dstroyed]

My ported shorty needs a lot more 3n38 than 7.8, mine is not an SVI.

Same here. I'm well over 9 grains of 3n38 before making it to major.

Me too but I was a little nervous to share that bit of info. Don’t forget YMMV!!

[jostein jensen]

I’m a little confused. Your first post said 5" then another said 4.5” Regardless, you know that you need to get your load over a chrono before going any further.

I said I aimed for 7,5 after advice from a guy that loads major 9 for a 5". If it was a confusing sentence I blame it on english being a second language

I know I need to chrono it before I do anything. I'm also going to talk to the smith who made it about the firing pin. third thing I'm going to do is fire a factory round through it and see if its the same result there! that would be a pointer to the firing pin not covering the hole being the cause.

thank you all for input!

[jostein jensen]

Okey new firing pin, long one, on order with a new ISMI extra strenght spring.

Chrono testing in daylight tomorrow.

[dstroyed]

great keep us up to date. I would like to learn more about what others are loading to with the 3n38. It seems that it is not too popular. It is hard to find so I'm sure that is part of it. i know it has me testing N350 and HS6.

[jostein jensen]

Nice semi overcast but clear weather, -2 degrees and good light at noon. Don't know if the weather and tempreature has much to do with the crony readings but anyway.

7.8gr 3N38, 30,6mm and 125gr MG JHP gave a 152 PF.

Will try 8.0 gr next saturday! Hopefully my new firing pin has arrived from Chuck by then

Here is a picture of the primer. Still Small Pistol.

Funny thing is, I'm not completely convinced its too much pressure causing it, cos here's one with factory Speer Lawman and I'm pretty sure factory rounds shouldn't have too high pressure signs???

[XRe]

Funny thing is, I'm not completely convinced its too much pressure causing it, cos here's one with factory Speer Lawman and I'm pretty sure factory rounds shouldn't have too high pressure signs???

The Lawman stuff is pretty hot IME, but, no, I wouldn't expect a pressure issue, there.... Its possible, in theory, that the throat is cut pretty tight in your gun, causing the bullet to be kissing the rifling when its in battery - that can cause the pressure to take a big jump. But, that's probably not the case (it'd have to be just right to cause the problem, but not cause issues with extracting a live round)...

I'm still thinking the longer firing pin will solve the flow issue for you... and again, that likely has nothing to do with the absolute pressure you're running... With a long FP, you could have significant pressure issues, and never notice an issue on the primer... Stick with the slower and more stable powders for best (ie, lowest pressure) results, there - if 3N38 is as readily available to you as it sounds, that one should serve you well in this regard. I wish we could get the VV stuff that cheap and easy over here

[jostein jensen]

The Lawman stuff is pretty hot IME

It holds 142 PF in my short and ported sweetheart, so I'll definitely agree on it being on the hot side for factory ammo.

Stick with the slower and more stable powders for best (ie, lowest pressure) results, there - if 3N38 is as readily available to you as it sounds, that one should serve you well in this regard. I wish we could get the VV stuff that cheap and easy over here

Its not exactly cheap... at $55 for a pound I think its robbery! But available it is

I'll update with the new firing pin installed and a tad more powder in next saturday, if the mail is fast enough

[al503]

Its not exactly cheap... at $55 for a pound I think its robbery! But available it is

At 9 grains, that's like .07 a round for powder.

That would be $ more than the bullet.

Edited November 10, 2007 by al503

[yoshidaex]

JJ,

Using your barrel as a case gauge, can you take a picture of the loaded round in the barrel? Like Dave mentioned, i'm wondering if the throating is cut deep for your barrel. Thats some serious primer flow and primer shearing. Make sure your firing pin channel is clean. When I was playing around with 3N38, 1.17" oal, 8.1 grains with 125 grain JHP zero bullet, I got a pf of 158. 9 grains got me to 170 pf. YMMV Sorry I can't remember what my primers looked like.

[jostein jensen]

He're is with my loaded ammo. Round dropped in and if i shake the barrel, the round jumps freely up and down.

here is the lawman factory round.

Is watching for flat shoulders the only way I can find out if I'm getting into dangerous pressures?

Edited November 10, 2007 by jostein jensen

[jostein jensen]

I'll update with the new firing pin installed and a tad more powder in next saturday, if the mail is fast enough

The mail was fast enough! Both Lawman and NATO ammo now has no primer flow. Didn't have time to squeeze out more ammo with more powder, so that'll be the next update.

[XRe]

Is watching for flat shoulders the only way I can find out if I'm getting into dangerous pressures?

There's a couple of things you can watch for - but by the time they show up, you're already running pretty hot pressure. A slight flattening of the primer shoulders is OK and expected. When they start looking like they've been melted and poured into the primer pocket, you're really running high pressures.

Also, beware of cases sticking in the chamber (seen as failures to extract where the old case is left in the chamber). That's usually a bad sign, as well - but failures to extract are not always a sign of stuck cases, so diagnose that one carefully, either way.

If you start to work up a load, and you hit a point where you're increasing powder charge, but not seeing an expected increase in velocity, or if you see a sudden surge in velocity, you're likely seeing pressure issues, as well. Things should roughly stay nice and linear (a certain charge weight change yields a roughly equal gain or loss in velocity).

I'm sure someone can think of a few others. Using 3N38, you've got a head start on the issue, cause you're using one of the slowest powders that will work for 9 Major. I used to make old Major (175 PF) using 130gr FMJs in a P9/EAA based gun, shooting SAAMI length 9x21 and using 540 (which is now available as HS-6) and 3N37 - either of those would be higher pressure than what you're looking at, and I didn't see melted primers or stuck cases then. But... I know that those loads were also rather stout on the pressure scale, so... tread carefully, but not fearfully...

So, the long firing pin fixed the flow??

[jostein jensen]

it fixed both flow and light strikes on everything else than SP's. I can shoot the CCI/Speer Lawman, which weren't reliable and even NATO which didn't fire even if I struck it several times.. The CCI's always fired on the second hit when they misfired on first attempt, but the NATO ammo never fired.

It now does on the first attempt.

But the light strikes were due to the pin being titanium, and the new one steel, so there was a mass issue with the titanium pin not giving enough ooomph!

[XRe]

But the light strikes were due to the pin being titanium, and the new one steel, so there was a mass issue with the titanium pin not giving enough ooomph!

In theory, the light pin should accelerate more, though, and have higher velocity. In a competition gun, a longer firing pin just gives you extra margin - there's more energy retained in the system at the point where the firing pin contacts the primer, and there's no "slack" for the firing pin to rebound into... etc, etc, etc... The extra mass probably doesn't hurt, either, in the end...

[Sestock]

Sorry bad connection and a double post.

Edited November 19, 2007 by Sestock

[Sestock]

Weren't the SV IMM guns designed to run on 3n38 only?

[Kingman]

Doug, they do tell you to use 3n38 only with them. Completely correct.

[Flatland Shooter]

[

Using 3N38, you've got a head start on the issue, cause you're using one of the slowest powders that will work for 9 Major. I used to make old Major (175 PF) using 130gr FMJs in a P9/EAA based gun, shooting SAAMI length 9x21 and using 540 (which is now available as HS-6) and 3N37 - either of those would be higher pressure than what you're looking at ..........

Good evening Dave,

I guess I'm a little dense this evening. I thought that slower powders, along with generating more gas, generate higher pressures to make major. If I read your comment correctly, HS-6 and 3N37 (both faster than 3N38) will generate higher pressures than 3N38?

Or are you refering to the old 175 PF generating higher pressures with these faster powders compared to a 160 PF Mr Jensen is now trying to achieve.

Like I said, I'm a little dense this evening, but if I do not have a correct understanding on powder versus pressure, I need to fix that.

Thanks.

Bill

[edwin garcia]

Weren't the SV IMM guns designed to run on 3n38 only?

Not exactly on all of them. Check out this link:

sv recommeded powder

[XRe]

I guess I'm a little dense this evening.

Yep... sorry

I thought that slower powders, along with generating more gas, generate higher pressures to make major.

Incorrect.

If I read your comment correctly, HS-6 and 3N37 (both faster than 3N38) will generate higher pressures than 3N38?

Correct.

Or are you refering to the old 175 PF generating higher pressures with these faster powders compared to a 160 PF Mr Jensen is now trying to achieve.

Doesn't matter.

Like I said, I'm a little dense this evening, but if I do not have a correct understanding on powder versus pressure, I need to fix that.

All powders push the bullet out of the barrel by generating gas, right? That gas volume creates pressure behind the bullet which pushes the bullet down the bore. A faster burning powder combusts faster - for some really fast powders, this happens even before the bullet begins to move. This also means that the peak pressure behind the bullet happens more quickly than a slower powder. The pressure curve on a faster powder tends to peak and then subside, some of them quite violently. If we go down to something as slow as N-105, the powder is still burning out in the comp, after the bullet is gone, and peak pressure builds gradually behind the bullet, peaking right before the bullet passes the first hole in the barrel.

That said, we're running medium to slow speed pistol/shotgun powders in our race guns - nothing as fast as Titegroup or Clays, for instance (at least, not for Major). All of these powders that we're using have some balance between those extremes. But, because the faster powder tends to have a higher peak pressure, we tend to have to run it at a higher peak pressure than a slower powder in order to get the same push as that gradually building huge cloud of powder that the slow powder generates. In some cases, depending on the burn rate, and the properties of the powder (how it responds to the interal dynamics of your loads), the peak pressure on the faster powder can become dangerously high. The rule of thumb re: things that a racegun cares about (pressure and gas) are that a faster powder has higher pressure and lower gas volume; a slower powder has lower pressure but higher gas volume - some guns like more of one than the other.

[Kingman]

The use of even a small quantity of incorrect ammunition in your IMM Open® can cause permanent damage to the gun.

Powder: The only powder we recommend for use with our IMM Open® firearms with hybrid holes or ports in the barrels is VV 3N38. There are no known substitutes at this time. Refer to the Vihta Vuori website for loading information. If you are using an older Infinity compensated firearm without hybrid holes or integral barrel ports which pre-dates the IMM series, or an IMM Open which does not have any hybrid holes or ports in the barrel, the "3N38 powder only" restriction does not apply.

quote from SVI's site

[Flatland Shooter]

Dave,

Thanks for the reply.

Bill

Edited November 20, 2007 by Flatland Shooter

[jostein jensen]

Update:

8.6gr 3N38, 30.6mm and 125gr MG JHP: 156,25 PF.

[ALF]

I have the same type of gun (SVI IMM) except that mine has three "hybrid holes". The load I use at the moment is VV N350 7,4 gn makes about PF 168 in my gun. I have also tried Vectan SP2 9,2 gn made about 168-170, and also Hogdon HS 6, 8,6 gn made a PF of 170.

N350 works great and is available almost everywhere in my neck of the woods(Sweden).

My gun came with a firing pin that was a little to short but I had it replaced and it has worked fine since then!

[jostein jensen]

I got some rounds with N350 in them from the previous owner. Didn't like the feel of them at all. It was fast but quite a bit of muzzle lift. I think the slower 3N38 works the comp a lot better, but its a lot more of it so it should